The present invention relates to a housingless type oil cooler formed by laminating a plurality of plate members and a method for producing the same.
For example, an apparatus described in Japanese Utility Model Unexamined Publication No. Hei-4-87726 (U.S. Pat. No. 5,099,912) is known as a housingless type oil cooler formed by laminating a plurality of plate members.
FIGS. 18 through 20 show an example of such a type of housingless type oil cooler.
In the drawings, the reference numeral 1 designates a core portion formed by alternately laminating first and second plates 3 and 5 made of aluminum. A composite tank 4 is mounted on the core portion 1. In the composite tank 4, a cooling water inlet tank 11 and a cooling water outlet tank 13 are formed by an upper casing 7 and a lower casing 9 made of aluminum. Two cooling water passage holes 15 provided in the first plate 3 are opened in the inlet tank 11 and the outlet tank 13 respectively.
Further, as shown in FIG. 20, through-holes 17 and 19 are formed in the respective center portions of the upper casing 7 and the lower casing 9 while a through-hole 22 communicated with one of two oil passage holes 21 provided in the first plate 3 is formed in the lower casing 9 so that the other oil passage hole 21 of the first plate 3 is blocked by the lower casing 9. Further, a cooling water inflow pipe 23 and a cooling water outflow pipe 25 are attached to the upper casing 7 so as to be disposed concentrically at a distance of 180.degree.. Respective insertion-side end portions 23a and 25a of the cooling water inflow and outflow pipes 23 and 25 are opened into the inlet and outlet tanks 11 and 13 respectively.
On the other hand, in a lower portion of the core portion 1, a lower plate 27, a reinforcement plate 29 and a mount plate 31 made of aluminum are disposed in order. Through-holes 33, 35 and 37 are formed in the center portions of the respective plates 27, 29 and 31 so as to be concentrical with the through-holes 17 and 19.
Further, in the side of these through-holes 33, 35 and 37, an oil inflow port 39 is formed so as to be opened into one of two oil passage holes 21 provided in the second plate 5. The other oil passage hole 21 of the second plate 5 is blocked by the lower plate 27. Further, second plate 5 side cooling passage holes 15, 15 are blocked by the lower plate 27. Further, a packing 41 is attached to a lower portion of the mount plate 31.
Further, through-holes 43 and 45 are formed in the center portions of the first and second plates 3 and 5 constituting the core portion 1. An oil outflow pipe 47 made of aluminum is attached in the two through-holes 43 and 45. Further, an oil return pipe (not shown) constituted by a stud bolt and fixed to a bracket (not shown) of an engine to form an oil outflow passage is inserted into the oil outflow pipe 47. The core portion 1 is fixed to the bracket by screwing a nut (not shown) with a screw portion (not shown) formed in an upper portion of the oil return pipe. Of course, a stud bolt formed by uniting the oil return pipe and the nut into one body can be screwed with the bracket.
Four through-holes are formed in the first and second plates 3 and 5 so as to be disposed at intervals of 90.degree. from their center portions. A pair of through-holes opposite to each other are provided as a cooling water passage hole 15 described above whereas the other pair of through-holes opposite to each other are provided as an oil passage hole 21 described above.
As shown in FIG. 20, cylindrical portions 57 and 59 are integrally formed in the outer circumferential edge of a plate body 3a of the first plate 3 and the through-hole edge thereof. Further, projection portions 61 and 63 projecting toward the plate body 3a of the first plate 3 are integrally formed in the outer circumferential edge of a plate body 5a of the second plate 5 and the through-hole edge thereof. As shown in FIGS. 19 and 20, the outer sides of the projection portions 61 and 63 of the second plate 5 are brazed to the inner sides of the cylindrical portions 57 and 59 of the first plate 3 so that a cooling water passage 65 is formed by the inner side of the first plate 3 and the inner side of the second plate 5 and an oil passage 67 is formed by the outer side of the first plate 3 and the inner sides of the cylindrical portions 57 and 59 of the first plate 3.
As shown in FIG. 20, in the cylindrical portion 57 of 5 the first plate 3, a large-size portion 69 and a small-size portion 71 are formed in the opening end side and the plate body 3a side respectively. Brazing is performed in the condition in which the large portion 69 of an upper first plate 3 is fitted in the small-size portion 71 of a lower first plate 3 adjacent to the upper first plate 3 so that a second plate 5 is disposed between the first plates 3.
In the aforementioned housingless type oil cooler, after non-corrosive flux is applied onto respective parts and dried in advance, the projection portions 61 and 63 of the second plate 5 are fitted to the cylindrical portions 57 and 59 of the first plate 3. Then, the large-size portion 69 of the first plate 3 is fitted to the small-size portion 71 of the other first plate 3 and the oil outflow pipe 47 is inserted in the through-holes 43 and 45 disposed at the center portions of these plates 3 and 5 to thus form a core portion 1. Thereafter, the lower plate 27, the reinforcement plate 29 and the mount plate 31 are attached to the upper and lower casings 7 and 9 and heated in a furnace to perform brazing of the respective parts. Thus, the housingless type oil cooler is produced.
In the aforementioned housingless type oil cooler, after cooling water from the cooling water inflow pipe 23 flows into the cooling water inlet tank 11, the cooling water passes through the cooling water passage holes 15 of the first and second plates 3 and 5 so that respective cooling water passages 65 are filled with cooling water. Then, the cooling water is subjected to heat exchange with the oil in the oil passage 67 and then flows out from the outlet tank 13 side cooling water outflow pipe 25.
On the other hand, oil from the engine side oil inlet passage (not shown) flows into the core portion 1 through an oil inflow port 39 disposed in a lower portion of the core portion 1. After the oil passes through respective oil passage holes 21 so that the oil passage is filled with the oil, the oil is subjected to heat exchange with the cooling water in the cooling water passage 65 and then flows into an oil outlet tank (not shown). Thereafter, the oil is cleaned by an oil filter disposed above the oil outlet tank and then flows out from the oil outlet passage (not shown) to the engine side through an oil return pipe.
The conventional housingless type oil cooler, however, has a structure in which oil and cooling water are made to go in and out separately in an upper portion of the core portion 1, so that oil inlet and outlet passages and cooling water inlet and outlet passages occupy space in the upper portion the core portion 1. Therefore, the oil outlet tank is formed by the upper and lower casings 7 and 9. To make the oil outlet tank communicate with the oil filter disposed on the upper casing 7, an opening hole is formed in the center portion of the upper casing 7. Accordingly, the upper casing 7 having the opening hole in its center is shaped like a cantilever which is left flexible freely at its center but supported by its periphery. In the housingless type oil cooler having such structure, when the oil filter is tightened strongly, the center of an oil filter seal surface 81 which is an upper surface of the oil filter is deformed so as to be bent like a cantilever. As a result, sealing between the oil filter and the oil filter seal surface 81 of the upper casing 7 of the housingless oil cooler cannot be secured so that there is a risk of occurrence of oil leaking.
Further, the upper casing 7 and the lower casing 9 are integrated with each other by brazing the respective bent cylindrical portions in the condition in which the respective bent cylindrical portions are disposed so as to be opposite to each other. However, because respective single articles of the upper and lower casings 7 and 9 are processed by press forming, spring-back occurs so that the forward end of each bent cylindrical portion is widened. It is therefore difficult to join the joint surfaces of the bent cylindrical portions, so that to secure brazing quality is made difficult. In addition, there is a requirement on design to secure the height size for attaching the cooling water inflow pipe 23 and the cooling water outflow pipe 25 to the lower casing 9. However, as described above, because the upper casing 7 and the lower casing 7 are assembled while the respective bent cylindrical portions are disposed so as to be opposite to each other and because the bending of the upper casing 7 is larger, poor accuracy in single articles at the time of press forming cannot be absorbed so that the height size of the upper casing 7 is increased. As a result, the size of the housingless type oil cooler cannot be reduced to compact size.
Further, the outer circumferential surface of the bent cylindrical portion of the lower casing 9 and the inner circumferential surface of the bent cylindrical portion of the upper casing 7 are joined by brazing. However, because the upper casing 7 and the lower casing 9 are processed by press forming, it is difficult to process the respective cylindrical portions thereof in the form of a true circle in section. As a result, a gap is produced between the joint surfaces so that there is a risk of occurrence of mixing of oil and cooling water caused by poor brazing.
As described above, because the outer circumferential surface of the bent cylindrical portion of the lower casing 9 and the inner circumferential surface of the bent cylindrical portion of the upper casing 7 are joined by brazing, the inner circumferential surfaces of the inlet and outlet tanks 11 and 13 of the casing 9 in which cooling water flows are provided as a brazing material layer. As a result, there is a problem in poor corrosion-resisting property.